Calculator for controlling basic oxygen steelmaking

ABSTRACT

A calculator designed for use by steelmakers in connection with the basic oxygen process and capable of quickly calculating the amount of oxygen and/or coolant that must be added to the basic oxygen furnace in order to produce a steel of a predetermined carbon and temperature level.

United States Patent 1 [111 3,757,092 Miller 1 Sept. 4, 1973 [S41 CALCULATOR FOR CONTROLLING BASIC 1,506,1l2 8/1924 Cutshaw 235/84 OXYGEN STEELMAKING 1,881,165 10/1932 Becker 235/70 2,307,967 1/1943 Stevenson.... 235/88 1 Inventor: Timothy Miller, p g, 2,422,663 6/1947 Feild 235/84 Pa. 3,016,190 1/1962 Baumann 235/84 3 25 419 121971 B 88 [73] Assignee: Bethlehem Steel Corporation, anon 235/ Bethlehem Primary Examiner-Richard B. Wilkinson [22] Filed Feb. 2, 1972 Assistant Examiner-Pat Salce 211 pp NOJ 222,736 Att0rneyJohn I. lverson 7 AB TRA T [52] US. Cl 235/74, 235/78, 235/88 [5 1 S C 15 1 1m. (:1. G060 A calculator designed for use y Steelmakers in [58} Field of Search 235/78, 85 R, 88, nection with the basic Oxygen Process and capable of 235 70 R, 4 quickly calculating the amount of oxygen and/or coolant that must be added to the basic oxygen furnace in 5 References Cited order to produce a steel of a predetermined carbon and UNITED STATES PATENTS temperature level- 1,214,040 1/1917 Jones 235/84 5 Claims, 2 Drawing Figures M NBSAXO PATENTEH 41973 3.757. 092

NOEHVO 7/1/11 7/! IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII l CALCULATOR FOR CONTROLLING BASIC OXYGEN STEELMAKING BACKGROUND OF THE INVENTION This invention relates to a calculator device for use in the refining of steel by the basic oxygen process. It is especially useful for calculating the amount of oxygen and/or coolant that must be added to the basic oxygen furnace during a reblow" in order to obtain a predetermined carbon and temperature level in the bath prior to tapping the molten steel from the furnace.

In the basic oxygen steelmaking process, molten pig iron and scrap are refined in a converter-like furnace by introducing substantially pure gaseous oxygen into the molten metal bath contained in the furnace from a watercooled lance positioned above the surface of the bath. Since the molten pig iron and scrap are refinedinto steel by this process'in a matter of minutes, it is often difficult for the operator to determine when the steel bath has been refined to the desired carbon and temperature level.

While a number of techniques, some of which use electronic computers, have been developed for controlling the basic oxygen process, the usual practice of obtaining the desired carbon and temperature level of the steel bath is as follows. First the flow of oxygen coming from the lance is stopped, the lance is withdrawn and the furnace tilted over on its side. Next a molten steel sample is obtained by reaching into the mouth of the furnace with a spoon. At the same time an expendable thermocouple is inserted into the bath to obtain a bath temperature measurement. The molten steel sample is allowed to solidify in a mold and is then sent to a laboratory for analysis. After the sample has been analyzed for carbon content, the results are sent back to the furnace operator. An alternative way of determining the carbon and temperature level of the bath is described in U. S. Pat. No. 3,574,598 issued Apr. 13, 1971 entitled Method for Controlling Basic Oxygen Steelmaking and assigned to applicants assignee.

Once the operator obtains the bath carbon and temperature measurements he is in a position to know whether to tap the furnace or resume blowing, i.e. reblow" with'the oxygen in order to obtain the desired carbon and temperature levels. Ifthe measurements indicate that a reblow is required, the operator must then calculate the amount of oxygen and/or coolant that should be added to the furnace to obtain the desired carbon and temperature levels for tapping the steel. The time required for these measurements and calculations is lost production time and even a few minutes is very costly to the steelmaker since many of the basic oxygen steelmaking furnaces now in use are able to produce several hundred tons of steel in less than one hour.

SUMMARY OF THE INVENTION It is an object of this invention to provide apparatus for calculating the amount of oxygen and/or coolant that should be added to a basic oxygen furnace during the course of a reblow in order to produce steel of a predetermined carbon and temperature level.

It is a further object of this invention to provide a simple, inexpensive hand operated calculating device that will quickly provide the operator with the amount of oxygen and/or coolant that should be added to a basic oxygen furnace during a reblow in order to produce a steel of a predetermined carbon and temperature level.

It has been discovered that the foregoing objects can be attained by apparatus preferably in the form of a disc-like calculator or circular slide rule comprising three superimposed discs and a cursor mounted for relative rotation with respect to each other. Each of the discs is provided with a scale to indicate carbon level, oxygen level and temperature level respectively while the cursor is provided with additional scales to indicate the effect of a coolant such as iron ore.

, BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the preferred embodiment of the apparatus of this invention.

FIG. 2 is a cross sectional view along lines 2-2 of FIG. 1 of the preferred embodiment of the apparatus of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the FIGURES and in particular to FIG. 1, I have illustrated to scale, a calculator l of this invention, suitable for use with a basic oxygen furnace having a steelmaking capacity of approximately 250-290 tons. The calculator l of this embodiment of my invention comprises three concentric superimposed discs mounted for relative rotation with respect to each other about a common axis pin 2.

The base disc 3 is of the largest diameter and has a scale 4 adjacent its periphery to correspond to carbon levels in the molten steel bath. This scale is based on empirical data available in any basic oxygen-steelmaking plant showing the efi'ect of oxygen in removing carbon at various bath carbon levels. The wider spacing of the values on the scale at the lower carbon levels indicates the well known fact that more oxygen is required to remove further carbon when the bath is already at a low carbon level. As shown in FIG. I, the carbon scale 4 extends from a carbon level of 0.03 percent to 1.40 percent, which range would includemost steels made today.

The second disc 5 is of a somewhat smaller diameter than the base disc 3 and has a linear scale 6 adjacent its periphery to indicate the amount of gaseous oxygen used. As shown in FIG. 1, the oxygen scale 6 extends from 250,000 standard cubric feet to 450,000 standard cubic feet which range includes the amounts of gaseous oxygen commonly used in refining 250-290 ton heats of steel by the basic oxygen process. Such scale could be designed to cover any range rather than the values shown in FIG. 1. Similarly the scale 6 could start at zero and cover only the amounts of oxygen blown during the reblow.

The third disc 7 is of a smaller diameter than the second disc 5 and has a linear scale 8 adjacent its periphery to correspond to the temperature of the molten steel bath. As shown in FIG. 1, the temperature scale 8 extends from 2,700 to 3,000 fahrenheit which range includes the bath temperatures common for steel made in basic oxygen furnace. From empirical data, it has been observed that the amount of bath temperature gained from blowing a given amount of oxygen is independent of the bath carbon level.

A cursor 9 is mounted for rotation about axis pin 2. The cursor 9 is provided with a first aperture 10 having a scale 11 along one edge adjacent to and cooperating with the temperature scale 8 on the third disc 7. The cursor 9 also has a second aperture 12 having a scale 13 along one edge adjacent to and cooperating with the oxygen scale 6 on the second disc 5. While I have illustrated the scales 11 and 13 positioned along one edge of aperture and aperture 12, if the cursor were made of a transparent material such as plastic, the apertures 10 and 12 could be omitted and such scales 111 and 13 could be imprinted directly on the transparent cursor 9.

Cursor 9 is also provided with a carbon index mark 15 adjacent to the carbon scale 4 on the base disc 3, and an oxygen index mark 16 at the beginning of scale 13 and a temperature index mark 17 at the beginning of scale 11. Index marks 15, 16 and 17 are shown as C 1,, OT and T 1 respectively on the cursor 9 illustrated in FIG. 1.

Scale 1 1 on cursor 9 is the coolant scale and as illustrated in FIG. 1 extends from 0 to 5,000 pounds of coolant, which generally is iron ore. Scale 11 is linear and is based on empirical data available in any basic oxygen steelmaking shop showing the effect of amounts of various coolants on bath temperature. The scale 11 could be designed for other coolants such as fluorspar or limestone as well. 4

If iron ore is to be used as the coolant, ore correction scale 13 is necessary on the cursor 9 to permit calculation of the amount of oxygen being added to the bath in the form of iron oxides, Scale 13 is merely based amount of available oxygen in the ore used. 7

The entire calculator l is preferably madeof a durable material such as plastic or metal with the various scales and indexes permanently printed thereon.

While I prefer to have the calculator of this invention in the form of a circular slide rule as illustrated in FIG. 1 for simplicity and compactness, it would be possible to arrange the various scales on a series of sliding bars with a sliding cursor, if desired. Y

The following is given as examples of the operation of the calculator shown in FIG. 1.

Suppose the steelmaker is attempting to make a 270 ton heat of steel which will tap 0.15% C and 2,900 F. Based on past experience or static charge calculations the operator will know that such a heat will require ap proximately 400,000 scf. of gaseous oxygen. Typically, a steelmaker might stop the blow when 90 percent or 360,000 scf. have been blown in order to take a bath carbon and temperature measurement as described above. Suppose the results of these measurements indicated that the bath was at the 0.50 percent C level and 2,850 F.

Using the calculator as shown in FIG. 1, the operator would set the value (360) for the amount of gaseous oxygen blown on oxygen scale 6 of disc 5 opposite the value (0.50 percent) for the test carbon measurement on carbon scale 4 of base disc 3 as shown in FIG. 1. Next using the temperature scale 8 on disc 7, the operator sets the value (2,850 F.) of the test temperature measurement opposite the value (360) for the amount of gaseous oxygen blown on the oxygen scale 6 of disc 5 as also shown in FIG. 1.

Next, holding the above settings by pinching the discs together, the operator moves the cursor 9 until the carbon index mark 15 (Cl) is opposite the aim or desired tapping carbon level (0.15percent). The total amount of gaseous oxygen required to reach this aim carbon level is read on the oxygen scale 6 opposite the oxygen mark 16 (01) on the cursor 9, which as shown on FIG. 1 is a value of 402,000 scf. The predicted tapping temperature after blowing 402,000 scf. of oxygen is read on the temperature scale 8 opposite the temperature index mark 17 (Tl). As shown in FIG. 1, this value is shown to be 2,935 F., which is 35 higher than the desired tapping temperature of 2,900 F. for this example.

Therefore, while holding the discs and cursor in place, the operator obtains from the coolant scale 11 or cursor 9, the amount of iron ore that must be added to the furnace to cool the bath to the desired level by observing the coolant value opposite the desired tapping temperature (2,900 F.) which as shown in FIG. 1 is a value of 2,400 pounds of ore.

Since an iron ore addition adds oxygen in the form of oxides to the bath, the operator using this calculation must discount the amount of oxygen in the ore from the gaseous oxygen blow. This is done by reading on the oxygen scale 6 the value (397,250 scf.) opposite the value (2.4) corresponding to 2,400 pounds of ore on the ore correction scale 13 on cursor 9.

As a result of these calculations using the calculator of this invention, the operator can see that he should blow an aggregate total of 397,250 scf. of gaseous oxygen and add 2,400 pounds of iron core to the bath in order for the heat to tap at the desired carbon level (0.15 percent) and temperature level (2,900 F.). Since at this point he had blown 360,000 scf. of gaseous oxygen already be subtracts the 360,000 scf. from the total calculated value of 397,250 scf. and thus determines he needs only to blow 37,250 scf. of oxygen more during the reblow.

To show further the use of this calculator, suppose the test carbon and temperature measurements in the previous example turned out to be a test carbon level of 0.50 percent C and a test temperature level of 2,800 F.

Using the procedures outlined in the previous example the operator would set the 360,000 scf. value in the oxygen scale 6 opposite the value (0.50 percent) for the test carbon measurement on the carbon scale 4 and the value (2,800 F.) for the test temperature measurement on the temperature scale 8. While holding these settings by pinching the discs the operator moves the cursor 9 until the carbon index 15 (Cl) is opposite the value of the aim carbon level (0.15 percent) on the carbon scale 4. As in the previous example, the total amount of gaseous oxygen required will be read on the oxygen scale 6 opposite the oxygen index mark 16 (O t), or 402,000 scf. The predicted tap temperature is read on the temperature scale 8 opposite the temperature index mark 17 (T1), or a value of 2,885 F.

Since the predicted tap temperature value (2,885 F.) is lower than 2,900 F. the operator must blow more oxygen to get the tap temperature up to the desired level. By moving the cursor 9 so that the temperature index 17 (TT) is opposite the aim tap temperature of 2,900 F. on the temperature scale 8, theoperator will read on the oxygen scale 6 opposite the oxygen index mark 16 (0 the value of 408,000 scf. Subtracting the 360,000 scf. already blown from the calculated value of 408,000 scf. indicates the operator must blow 48,000 scf. during the reblow.

Since the additional oxygen being added to raise the temperature will remove additional carbon, the operator will know from the carbon scale 4 opposite the carbon index mark 16 (Cl) that the tap carbon level will be 0.125 percent C. which is lower than the aim carbon level of 0.15 percent. However this can be easily made up by adding carbon to the ladle during tapping.

Thus for this second example, the operator must blow 48,000 scf. during the reblow to give a total of 5 408,000 scf. of gaseous oxygen, adds no iron ore coolant, but adds 0.25 percent C to the ladle during the tapping to compensate for overblowing to achieve the desired temperature.

These two examples illustrate the versatility of the calculator of this invention to the steelmaker. By simple manipulation of the calculator the operator is quickly provided with the information required to tap molten steel from the basic oxygen furnace at predetermined carbon and temperature levels.

While I have shown my invention by illustrating and describing the preferred embodiment of it, I have done so by way of example, and am not to be limited thereby as there are modifications and adaptations that could be made within the teachings of this invention.

I claim:

1. A disc calculator comprising a plurality of superimposed concentric discs mounted for relative rotation with respect to each other about a common axis comprising a base disc having a first scale adjacent its periphery, a second disc of smaller diameter than said base disc and having a second scale adjacent its periphery and a third disc of smaller diameter than said second disc and having a third scale adjacent its periphery, and a cursor mounted for rotation about said axis, said cursor having a fourth scale adjacent said third scale and cooperating therewith and a fifth scale adjacent to said second scale and cooperating therewith and an indexing mark adjacent to the periphery of said base disc and to said first scale and cooperating therewith, said indexing mark radially aligned with the beginning of said fifth scale.

2. The calculator of claim 1 wherein the first scale represents amounts of carbon, the second scale represents amounts of gaseous oxygen and the third scale represents temperature.

3. The calculator of claim 1 wherein the fourth scale on said cursor represents amounts of coolant.

4. A calculator comprising a first member provided near its edge with a first scale, a second member movable with respect to the first member and provided near its edge with a second scale, a third member movable with respect to said second member and provided near its edge with a third scale, and a cursor movable with respect to said first member, second member and third member and provided with a fourth scale adjacent to said third scale and cooperating therewith and a fifth scale adjacent to said second scale and cooperating therewith and an indexing mark adjacent the edge of said first member and to said first scale and cooperating therewith, said indexing mark aligned with the beginning of said fifth scale.

5. The calculator of Claim 1 wherein the cursor extends over the peripheral edge and across the back of said base disc and is secured at two points to said common axis. 

1. A disc calculator comprising a plurality of superimposed concentric discs mounted for relative rotation witH respect to each other about a common axis comprising a base disc having a first scale adjacent its periphery, a second disc of smaller diameter than said base disc and having a second scale adjacent its periphery and a third disc of smaller diameter than said second disc and having a third scale adjacent its periphery, and a cursor mounted for rotation about said axis, said cursor having a fourth scale adjacent said third scale and cooperating therewith and a fifth scale adjacent to said second scale and cooperating therewith and an indexing mark adjacent to the periphery of said base disc and to said first scale and cooperating therewith, said indexing mark radially aligned with the beginning of said fifth scale.
 2. The calculator of claim 1 wherein the first scale represents amounts of carbon, the second scale represents amounts of gaseous oxygen and the third scale represents temperature.
 3. The calculator of claim 1 wherein the fourth scale on said cursor represents amounts of coolant.
 4. A calculator comprising a first member provided near its edge with a first scale, a second member movable with respect to the first member and provided near its edge with a second scale, a third member movable with respect to said second member and provided near its edge with a third scale, and a cursor movable with respect to said first member, second member and third member and provided with a fourth scale adjacent to said third scale and cooperating therewith and a fifth scale adjacent to said second scale and cooperating therewith and an indexing mark adjacent the edge of said first member and to said first scale and cooperating therewith, said indexing mark aligned with the beginning of said fifth scale.
 5. The calculator of Claim 1 wherein the cursor extends over the peripheral edge and across the back of said base disc and is secured at two points to said common axis. 